Be aware that what you see in Print Layout (or even in Print Preview) may not be what will print. When you insert an Odd Page/Even Page break, Word will insert a totally blank page as needed. As mentioned, you cannot have an odd page number on an even page
(and vice versa). If you have five pages of front matter (i-v), you need to have a blank page vi, followed by 1 on a recto page.
I discourage use of the gutter because it makes no sense to me. When you are creating a book, you are (presumably) already using "Mirror margins." That being the case, you can just add to the Inside margin instead of using a gutter. But Print Layout view
is deceptive because it does not show you facing pages, and it does not display the blank pages that Word inserts. If you have enabled either "Mirror margins" or Different Odd and Even headers/footers, then you can display two pages in Print Preview and see
the blank pages. You can't use the Print Preview in the Backstage (Print Preview and Print); you must add Print Preview Edit Mode to the Quick Access Toolbar; that one will show you facing pages including the blank ones.